Science Daily Magazine has an article about there being a lot more free floating planets in our galaxy than there are stars. I don't know about that, it is certainly possible that a lot of planets are out there. Ethan Siegel in his "Starts With A Bang" blog has a post about how Jupiter size planets that form close to their parent stars will throw smaller planets out of that solar system. So there can be a huge number of free-floating planets out there.

Where I have a problem with the article is that the researchers who wrote the paper that is being reported on say that lots of those planets are life bearing. That rings alarm bells for me. First off, they say that these planets formed in the early universe, when it was only a few million years old. I'm not sure how life would have formed at that early age, since the concentration of heavier elements would have been much lower than it is now. The other problem is that I'm not sure how life would have formed at the low temperatures free floating planets would encounter.

Bill Gill

That really isn't a problem. It is a matter of scale. Assume Jupiter is an average planet size (143,000 km). There are bigger and smaller, but let's use that for thinking. The nearest star (other than our sun) is about 4.4 light years. That is 41,598,721,804,147.2 km. Rounding that off we get about 41E9 km between us and the nearest star. Jupiter's size would round to 143E3 km. So roughly 3E5 Jupiters could fit in that distance. And that is linear, actually the free floating planets would be all round. So there isn't any problem with our distant vision being obscured by free floating planets.

Bill Gill

Hi Saffyro. Re free-floating planets bumping into each other:

A few billion years from now, the Andromeda galaxy is expected to merge with the Milky Way. Each of them contains - at a minimum estimate - 100 billion stars. Yet simulations have shown that very few stars, possibly none, will collide; such is the immensity of the space between them. Our entire solar system, were it to be intact at that time, would be expected to remain intact, even though it might be ejected, as a whole, from the galaxy. That seems to suggest that perhaps collisions between free-floating planets might also be rare.


Bill

Even better when you correct it Bill: 4.16E13 km, so about 3E8 (300,000,000) Jupiters. I'm not sure that it's easier to visualize, but if you scale down Jupiter to the size of tennis ball, then the nearest star would be as far away as the Moon

I would take all bets ... free money :-)

Well, I was afraid I had gotten it a little wrong, I just whipped through the calculation in my head real fast instead of actually working it out. I didn't think I got it that far off.

Bill Gill